AU-20000 Question

[ckelly]

Fred

This is taken from an answer you gave Night Wolf,


Well, its simply that the Volume control is in 3db increments all the way around the dial from left to right on the AU-20K: -60,
-57, -54.... and so on till 0DB. Compare that to other models where the rate of DB change is typically greater- such as: -60, -54, -48, -42, -38.... thus, to get to -30DB on the AU-20K requires that the Volume control be turned up past halfway mark whereas on the others, -30 DB is located at the 10 oclock postion. But make no mistake about it- the AU-20K IS powerful- it maintains the 3db increment whereas the others fall off, so while they peak out at some point, the AU-20K continues to pump it out.


Those 3 decibel increments in the volume control are to avoid clipping the speakers?

Chris

[BeatleFred]

Hi Chris:

Regarding the 3DB increments: What you mentioned about Clipping is what I had thought of as well for the reason of why it was designed that way.

Keep in mind, the AU-20000 was introduced in late 1975 along with the BA-5000, BA-3000 and CA-3000- the elite Definition Series models. These models are a HUUUUUGE step up compared to everything that Sansui made before it. For example, in the early 70's, Sansui just had the BA-60 power amp which was 60W- and I'm pretty sure thats 60W ihf rating, not rms. Now, all of a sudden in late '75 Sansui unleashes a HUGE, 108 pound, 300 Watt rms monster of a BA-5000. So, as I said, that is a BIG step up!

And at 170 Watts the AU-20000 is quite a step up from all previous Sansui integrated amps. So, my Point is: Maybe Sansui did decide to design the Volume Control to rise more gradually in order to prevent some naive person at the time who was checking it out at his local audio shop from quickly turning the Control up and blowing out whatever speakers were hooked up to it. I cant say for certain if this was the rationale behind the Volume Control calibration- if I could turn back the clock and email /Internet existed, you can be sure I'd contact a Sansui representative and ask him. (Or actually, being there was a Sansui building not far from here, in Woodside New York, back at the time when those models came out, an 11 yr old Freddy here, couldve visited them):) Or even Lyndhurst, New Jersey in the 80's for that matter- Sigh.... if I had only known I would be the
Sansui dude I am now- that wouldve been a dream job to work there, right?:) They would have HAD to hire me- 'cause I would probably drive them nuts with calls to their office or personal visits every day! :)

The reason why I'm borderline in my answer about the 3DB control - to prevent clipping: because the thought now occurs to me to recheck the AU-11000 and AU-9900 and see if they use the 3DB calibration. They are 110W and 80W respectively. When I was looking thru some of my catalogs the other day, I thought I did notice in one of the photos (that is more close-up to be able to make out the Volume numbers), that they also were 3db incremented. If thats the case on these lower wattage amps, that might tend to dismiss the Clipping hypothesis. These models came out after the Defintion Series in 1977 along with the CA-2000 preamp. An interesting observation I noted was that they did keep the AU-20K in the Product Line for another year- and so they moved it into the Professional Series along with the AU-11000, 9900, and CA-2000. A "demotion" from the Defintion Series? :) I'd also like to mention the two can be distinguished in that the Defintion's had the beautiful burgundy top, the Prof's were gray. The Volume control on the CA-2000 though is non- 3db. BeatleFreddy here, will be noting all of these various and unique model attributes and I will probably post them on a Sansui webpage./ite of my own or on Isao's sansui.us site. Another observation I would add to the List of "Sansui Mysteries" while we're on the subject of Volume Controls- check out the 9090DB Line- have you ever noticed there are NO numbers at all around the control?! 'Fess up now- those of you who werent aware of it before- to all of you'ze I say "Glasshopper, you rook, but you do not see!" :)

Otherwise, perhaps the answer just is being these models were the ahem, "upper class" ones, that Sansui wanted the design to be, how shall we say, more "a-la naturale", if you think about it- that is the natural way it should be- if you want the music heard LOUD, the Volume Control then should also be moved correspondingly higher. The other way (faster sound level increases, earlier in the volume knob turn) , though far more commonly used, is more unnatural in accordance with the logarithmic nature of human hearing. I think the constant 3db all the way throughout from -60 to 0 gives a more smooth level increase - and its certainly consistent throughout the entire range.

Hmmm... does any University out there offer a Masters Degree or PHD in Sansui-ology? :)

Regards, B/F "Pure Power"

[ckelly]

Thanks Fred

As usual, your answers are clear you are DA MAN for all things Sansui :ntwrthy:

I see - the 3db increases are to make the volume control more linear, rather than logarithmic, cool feature.

as for the 9090db not having numbers on the volume knob - I could of answered that by calling my buddy who has one :huge: ; he just got it back from the tech after SIX MONTHS :eek:

[Glenz75]

HI Fred :) Hey I just had a quick look at my AU-9900 while chomping down breakfast..hehe, it looks like the volume increments are -2db steps, and yeah the vloume control works the same as the AU20000, you've got to turn the knob virtually to 1/2 way before the sound really takes off, but at low level listening, i quite like the linear fashion of the volume, rather than turning the knob a few notches and have it blare out loud music! hehe..
Cheers
Glen :)

[Lefty]

Hi BF;

Well I think you got the basic idea down pat. I'll just try and simplify if some.

Most applications for pots are for straight linear applications. That is 50% position on pot gives 50% of voltage output at the variable tap. However for audio volume applications we need a logrithmic taper because of human hearing is a log function.

Therefor pot manufactures make log taper pots that try to approximate the log function, however they are not very accurate and some rise too quick and some too slow. Now if a manufacture wants to design a accurate calibrated volume control it can be done but generaly requires additional fixed resistors in addition to the pot itself. So if one sees a volume control that is calibarted in DB units you know that the manufacure went to the extra effort to attain that goal.

Also by definion how load a given amp is vs it's pot position is no indication of it's total power or quality, just it's particular control's taper.

Here is the best reference I have come across to explain the theory and application of pots in general and as volumn controls.

http://sound.westhost.com/pots.htm#taper


Lefty

[BeatleFred]

Hi Chris- Luckily I highlighted that whole message and copied it- this Site still likes to Log you out if you spend some time typing in a long message. Very glad I didnt lose it. Its easy for others to do the reading- but thinking of what you want to write and typing it all in- thats Work for the writer:)

Anyway, I think you might have linear and logarithmic reversed. Perhaps my explanation contributed to that- but again, typing in every thought is very time consuming, sometimes I have to just rely on others who are reading to use their intuition to interpret what I'm saying.

I mentioned this example before which I thought was a good way to explain it. I am a big fan of the use of Analogy to make something thats complicated or has too much technical mumbo-jumbo, easier to understand. The example for Linear vs Logarithmic I use is the airplane analogy. If youve read it before- disregard. Otherwise, its simply that if you were to stand next to a jumbo jet on a runway- and say, its sound pressure level is measured to be, 130DB. What would the SPL be if a 2nd plane came along and parked alongside the first jet? The answer is not 130 + 130= 260DB. That would be a linear relationship. The answer is 133DB which is logarithmic. One plane is 130DB. Two planes are 133DB. There is a 3DB increase - not another (linear) 130 DB increase. Its good that Mother Nature made human hearing this way- 2 planes and 260DB would result in destroyed eardrums:)

Do you see how something is made alot more comprehensible through the use of analogy- rather than heavy technical math equations? Ive studied (and forgotten) alot of Math when I was an EE student- so while I do appreciate Math, I am more impressed by someone who can take a technical concept and explain it in easier terms rather than someone who just throws math equations all over the place. Memorizing math formulas will only result in them being forgotten in Time whereas understanding Concepts- you will remember them alot easier.

[BeatleFred]

Hi Lefty:

You posted while I was engrossed in writing my message above, so I didnt see your message until just now. Thanks for the Link you provided- I emailed that site to myself for further reading, I'm sure there's alot of good info there.

Glen: -2db steps, hmm, interesting. starts at -60? Then -58,
-56, and so on until 0 ? I probably can find a photo of it in one of my manuals, or catalogs, or a pic Online- but if you can confirm that now, would save me some time. I just knocked myself out yet again to reorganize all of my catalogs in folders and put back neatly in closet- I'd like to atleast keep them staying neat for a lil' while longer, rather than to go back and mess the place up again searching for info. Its a never ending process: Mess, Clean Up. Mess again, Clean Up again...:)

But anyway, observing how the Volume control is designed on various models is interesting. The click stops on the AU Sansui's are very nice. I believe my Pioneer SX-980 has a db caibrated control, gonna have to take another look when I have a chance.

Regards, B/F.

[Glenz75]

Hi Fred, yes its definetly in -2b increments I just went and double checked on that, but not sure if the AU-11000 is the same as its wattage is slighty higher.. I know someone who owns a AU11000 so next time I speak to him I'll get him to rattle off the db steps.
I've re-posted that Pioneer serial number dating thing again too for those who are interested.
Cheers :)

[Lefty]

The Decibel units has an interesting history. Alexander Bell in his early studies of audio that lead to the telephone and first prerecoded records came up with the need for a logrithimic scale that approximates human hearing. So he did lots of hearing tests with large number of people and defined the unit DB as the smallest detectable increase that the AVERAGE person could detect. So the bel in decibel is to honor Mr. Bell.

Certainly there will be some variation in individuals hearing ability, hence the real possiblity of 'golden ears' ;)

As a recommendation for serious audio blind testing it is suggested that all level matching be done to +/- .1 DB so account for people's variation of hearing sensitivity...

[ckelly]

My AU-555 has a standard volume pot, the sound increment on lower levels increases a lot, as you go higher the "loudness" increases are smaller.

So, lemme see if this hungover brain can understand :stupid: - the volume pot on the AU-20,000 is even all the way through? If that is the case, does that mean it's antilogarithmic?

Chris

[VinylHanger]

My G-22000 starts with an 8 db, then a 5, then a 3 then 2's until it gets to 12 then it is ones. So it is wieghted in the beginning which sucks. I can't even turn it up past 9 o'clock and it blows the paint off the walls. Putting it on the first notch is too loud for early morning listening.

[BeatleFred]

You can always switch the G-22000 to power amp mode and drive it with a CA-3000 preamp to get the 3DB Volume:)

[BeatleFred]

Then again, if its docked together via those cables, the CA-3000 idea wouldnt work. You'll just have to "suffer" with the G-22K as it is:)

[bully]

I do remember that a couple of mine were calibrated in -2dB increments. I'll try to remember to find the OM(s).

pete :dunno:


*Think* before writing/speaking :dunno:

[bolly]

This one doesn't have a stepped volume attenuator...